1. Field of the Invention
This invention relates to medical therapeutic apparatus. More particularly, this invention relates to electronic circuitry for use in an external defibrillator apparatus. The apparatus of this invention provides an improved, low cost, portable external defibrillator.
2. Background Information
The external defibrillator is a well recognized and important tool for resuscitating cardiac arrest patients. Defibrillation of the human heart is accomplished by applying an electrical waveform to the cardiac muscle with appropriate electrodes, causing the cessation of rapid uncoordinated contractions of the heart (fibrillation) and restoration of normal beating of the heart.
In the past, external defibrillators have been limited in use to hospitals, ambulances and other specialized locations. However, the health care community has recently called for more widespread disposition and use of automatic external defibrillators, particularly those which are portable. For example, it has been recognized that the placement of portable external defibrillators in nursing homes, sports facilities, and various other public and private facilities could save many lives in the setting of a cardiac arrest. Another proposal for the widespread placement of portable external defibrillators is with public safety officials such as police squad cars and the like.
A primary factor in limiting the dissemination of portable external defibrillators is their cost. A typical portable external defibrillator costs approximately $5,000 to 10,000. Costs for portable external defibrillators are high mainly due to the high costs of circuit components which are able to deal with extremely high voltages and currents utilized in cardiac defibrillation.
Despite the need in the art for a portable external defibrillator apparatus and circuitry therefor which overcomes the limitations and problems of the prior art, none insofar as is known has been proposed or developed. Accordingly, it is an object of the present invention to provide a portable automatic external defibrillator apparatus which overcomes the limitations and shortcomings of the prior art. Particularly, it is an object of this invention to provide an improved portable external defibrillator apparatus which is reliable, durable, and effective at delivering defibrillating charges to the body of a patient. Another object of this invention is to provide defibrillation circuitry which is inexpensive to construct so that portable external defibrillators may be disseminated in a variety of settings and locations and for use by a variety of skilled and semiskilled medical personnel. A specific object of this invention is to provide circuitry for charging a plurality of capacitors in parallel and for discharging them in series which utilizes a plurality of semiconductor switches.